A traffic jam is seen as people evacuate after tsunami advisories were issued following an earthquake, in Iwaki, Fukushima prefecture, Japan, in this photo taken by Kyodo November 22, 2016. Kyodo/via REUTERS

By Yuka Obayashi and William Mallard | TOKYO
A powerful earthquake rocked northern Japan early on Tuesday, briefly disrupting cooling functions at a nuclear plant and generating a small tsunami that hit the same Fukushima region devastated by a 2011 quake, tsunami and nuclear disaster.

The magnitude 7.4 earthquake, which was felt in Tokyo, sent thousands of residents fleeing for higher ground as dawn broke along the northeastern coast.